Infrared studies on rotational isomerism. III. 2-Chloro- and 2-bromo-ethanol

1969 ◽  
Vol 47 (6) ◽  
pp. 901-910 ◽  
Author(s):  
Paul Buckley ◽  
Paul A. Giguère ◽  
Michel Schneider
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Rotational Isomerism ◽  
Apparent Discrepancy ◽  
Trans Isomers ◽  
Kcal Mole ◽  
Infrared Studies ◽  
Isotopic Molecule ◽  
Intramolecular Hydrogen ◽  
Unambiguous Assignment

The relative intensities of the C—X stretching bands of the gauche and trans isomers in the vapor were measured as a function of temperature up to 165 °C for 2-chloroethanol, and up to 130 °C for 2-bromoethanol. From these the enthalpy differences between the two isomers were found to be 1.20 and 1.45 ± 0.1 kcal mole−1 respectively for the two halogenated ethanols. Similar measurements on the O—H stretching bands gave values higher than the above by 0.45 kcal mole−1 for both compounds. This apparent discrepancy is interpreted as due to a second gauche isomer, the OH group of which is not engaged in intramolecular hydrogen bonding, and which is less stable than the trans isomer.A study of the isotopic molecule ClCH2—CH2OD has led to unambiguous assignment of the OH bending and torsional frequencies. The spectra of the solid show that 2-chloroethanol can exist in two different crystalline phases: a stable one consisting of gauche molecules only, and a metastable one containing both isomers.

Infrared studies on rotational isomerism. IV. 2-Cyanoethanol

1969 ◽  
Vol 47 (24) ◽  
pp. 4685-4690 ◽  
Author(s):  
Michel Schneider ◽  
Paul A. Giguère
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Rotational Isomerism ◽  
The Other ◽  
Trans Isomers ◽  
Kcal Mole ◽  
Infrared Studies ◽  
Enthalpy Difference ◽  
Temperature Deposition ◽  
Intramolecular Hydrogen

From the infrared spectra of the vapor measured between 4000 and 200 cm−1, 2-cyanoethanol was found to exist as gauche and trans isomers in roughly equal proportions around 100 °C. The gauche form is the more stable of the two, as in 2-chloro- and 2-bromo-ethanol, but the enthalpy difference is less than half as large; at most 0.7 kcal mole−1. This indicates some weak (about 1 kcal mole−1) intramolecular hydrogen bonding between the OH group and the π electrons of the C≡N bond.In the solid, two distinct crystalline phases have been observed. Crystal II, consisting of gauche molecules only, is normally obtained; for instance by annealing the vitreous solid from low temperature deposition of the vapor. Crystal I, which contains the two isomers, may be obtained irreversibly from the melt of crystal II under controlled conditions.On the other hand there was no indication in the spectra of a cyclic tautomer as suggested recently.

Infrared studies on rotational isomerism. II. 2-Fluoroethanol

1968 ◽  
Vol 46 (18) ◽  
pp. 2917-2923 ◽  
Author(s):  
Paul Buckley ◽  
Paul A. Giguère ◽  
Daijiro Yamamoto
Keyword(s):  
Intramolecular Hydrogen Bonding ◽  
Rotational Isomerism ◽  
Condensed Phases ◽  
Frequency Range ◽  
Trans Isomers ◽  
Kcal Mole ◽  
Solid States ◽  
Infrared Studies ◽  
Free Molecules ◽  
Intramolecular Hydrogen

The infrared spectra of CH2FCH2OH were measured in the vapor, liquid, and solid states from 4000 to 200 cm−1. The Raman spectrum of the liquid was also measured over the same frequency range. From the results it appears that the free molecules exist almost entirely in the gauche configuration, which is stabilized by intramolecular hydrogen bonding. Only in the vapor at temperatures above 60 to 70 °C is there any indication of weak bands due to trans isomers. In the condensed phases the molecules are associated through strong hydrogen bonds (3–4 kcal/mole).

Beziehungen zwischen Rotationsisomerie, Wasserstoffbrücken-Bindung und Substituenteneffekten der organischen Chemie / Relations between Rotational Isomerism, Hydrogen Bonding, and Substituent Effects in Organic Chemistry

1972 ◽  
Vol 27 (6) ◽  
pp. 663-674 ◽  
Author(s):  
Gotthard H. Krause ◽  
Herbert Hoyer
Keyword(s):  
Hydrogen Bonding ◽  
Substituent Effects ◽  
Intramolecular Hydrogen Bonding ◽  
Rotational Isomerism ◽  
Proton Acceptor ◽  
Single Bond ◽  
Free Enthalpy ◽  
Acceptor Group ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

The change of free enthalpy involved in intramolecular hydrogen bonding is smaller if the proton acceptor group can rotate round a single bond, as compared to proton acceptor groups which are fixed in a position optimal for hydrogen bonding. Also, the free enthalpy change is altered when the rotation of the proton acceptor is sterically restricted. This is demonstrated by comparing the absorptions of carbonyl stretching vibrations in the infrared spectra of certain compounds showing rotational isomerism. In the present study derivatives of 5-hydroxy-2,2-dimethyl-6-carbomethoxychromanone- (4), 3-nitrosalicylaldehyde and 3-nitro-2-hydroxy-acetophenones substituted in the position 5 and 6 are examined.

Vapour phase infrared studies of alcohols - I. Intramolecular interactions and self-association

1973 ◽  
Vol 335 (1600) ◽  
pp. 97-111 ◽  
Keyword(s):  
Hydrogen Bonding ◽  
Infrared Spectra ◽  
Path Length ◽  
Intramolecular Hydrogen Bonding ◽  
Vapour Phase ◽  
Intramolecular Interactions ◽  
Argon Matrix ◽  
Infrared Studies ◽  
Self Association ◽  
Intramolecular Hydrogen

Infrared spectra are reported of methanol, ethanol, propan-2-ol, 2-methylpropan-2-ol, 2, 2, 2-trifluoroethanol, 2, 2, 3, 3-tetrafluoropropan-1-ol and 1, 1, 1, 3, 3, 3-hexafluoropropan-2-ol in the vapour phase in a 1 m path-length cell at pressures up to the s. v. p. of the alcohol. Also reported are 40 m path-length vapour and argon matrix spectra of trifluoroethanol. Dimer absorptions are identified for all the alkanols and for trifluoroethanol, and some estimates of ∆ H provided. Trifluoroethanol exhibits a striking series of sum-and-difference bands of the OH stretch with other fundamentals, 14 summation modes being observed extending in frequency to over 5000 cm -1 and involving most of the fundamentals below 1500 cm -1 . Other fluoroalcohols with fluorines substituted on β carbon atoms exhibit similar sum-and-difference modes. The alkanols exhibit only one such pair of bands due to the OH stretch plus or minus the OH torsion, and this provides a convenient method of measuring the torsional frequencies. The different behaviour of the fluoroalcohols is attributed to intramolecular hydrogen bonding.

Infrared Studies on Rotational Isomerism. V. 2-Nitroethanol

1971 ◽  
Vol 49 (23) ◽  
pp. 3815-3820 ◽  
Author(s):  
Paul A. Giguère ◽  
Tokiji Kawamura
Keyword(s):  
Hydrogen Bond ◽  
Crystalline Phase ◽  
Raman Effect ◽  
Rotational Isomerism ◽  
The Other ◽  
Trans Isomers ◽  
Definite Evidence ◽  
Pure Sample ◽  
Infrared Studies ◽  
Intramolecular Hydrogen

The i.r. spectra of 2-nitroethanol in the three physical states were measured between 4000 and 250 cm−1. The liquid and the crystal were also studied in Raman effect. In all three states the molecules exist as gauche and trans isomers, the former being stabilized by a weak intramolecular hydrogen bond. Definite evidence for a third isomer, previously reported in dilute CCl4 solutions, could not be ascertained from the vapor spectra as a function of temperature. On the other hand this study revealed appreciable decomposition of the vapor above 80 °C, with formation of nitroethylene and also some aldehyde. For that reason it was not possible to evaluate the enthalpy of isomerization. The difficulty of securing a pure sample of 2-nitroethanol is emphasized. Only one crystalline phase was obtained.

Theoretical study of intramolecular hydrogen bonding and molecular geometry of 2-trifluoromethylphenol

10.1002/jcc.2 ◽  
1996 ◽  
Vol 17 (16) ◽  
pp. 1804-1819 ◽  
Author(s):  
Attila Kov�cs ◽  
Istv�n Kolossv�ry ◽  
G�bor I. Csonka ◽  
Istv�n Hargittai
Keyword(s):  
Hydrogen Bonding ◽  
Theoretical Study ◽  
Molecular Geometry ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen
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